Floor space in a semiconductor clean room manufacturing facility can be very expensive from a footprint (area) prospective. To minimize the cost of fabrication, some processing tools increasingly employ a more compact design having a stacked module vertical architecture. Such a stacked approach of electrochemical plating cells may increase the effective tool output per unit area and reduce the effective implementation costs when amortized over the life of the tool. The Sabre3D™ plating system by Lam Research Corporation of Fremont, Calif., is an example of a two level stacked plating module architecture. Wafer processing systems using condensed fluid in a mixed phase environment (e.g., air/gas exposed to liquid) often use circulation to recycle and reuse the operating fluids. This circulation may entrap and create bubbles and foam in the liquid during circulation of the fluid from one portion or region of the tool to another. While certain techniques have been developed to minimize the impact of these bubbles (e.g., including a degasser in a fluid feed line), these techniques are generally costly to implement. As such, methods and apparatus for preventing the introduction of gas into the processing fluid are desired.